The 1-phenyl-1-diethylaminocarbonyl-2-phthalimidomethyl-cyclopropane-Z serves as an important precursor for the manufacture of MILNACIPRAN (D.C.I.), a drug useful in the treatment of depression and which has Formula II ##STR2## from which it is prepared by splitting off the phthalimido group and conversion to the hydrochloride salt, advantageously using an alkanolamine such as ethanolamine and hydrochlorinating in conventional manner according to EP published application 0200638 published Nov. 5, 1986.
In the prior art, illustrated by F 2,581,059, the compound of Formula I is prepared in several steps from 1-phenyl-2-oxo-3-oxa-bicyclo(3:1:0)hexane in a yield of about 50%.